Publish WithExactlyOnceQoS with 2 Clients and 1 Broker in the same application results in disconnects

Describe the bug

When publishing a message with QoS “WithExactlyOnceQoS” the Client gets disconnected immediately after the receipt of the message. QoS “WithAtMostOnceQoS” works as expected.

Which project is your bug related to?

• ManagedClient
• Server

To Reproduce

run program below, change QoS in Line 87

Expected behavior

Client should not disconnect after message receipt.

Screenshots

Expected

Current

using MQTTnet;
using MQTTnet.Client.Options;
using MQTTnet.Extensions.ManagedClient;
using MQTTnet.Server;
using System;
using System.Text;
using System.Threading.Tasks;

namespace MQTTnet_Test1
{
    class Program
    {
        private IMqttServer LocalServer;

        static void Main(string[] args)
        {
            var p = new Program();

            p.StartServer();

            var client1 = p.StartClient("client1");
            var client2 = p.StartClient("client2");

            Task.Delay(1000);

            var message = new MqttApplicationMessageBuilder().WithTopic("topic1").WithPayload("Hello World").WithExactlyOnceQoS().WithRetainFlag().Build();

            client1.PublishAsync(message);

            Console.ReadLine();
        }

        private void StartServer()
        {
            var optionsBuilder = new MqttServerOptionsBuilder().WithConnectionBacklog(100).WithDefaultEndpointPort(1883);
            LocalServer = new MqttFactory().CreateMqttServer();
            LocalServer.StartAsync(optionsBuilder.Build());
            LocalServer.UseClientConnectedHandler(evt =>
            {
                Console.WriteLine(string.Format("SERVER - Client connected {0}", evt.ClientId));
            });
            LocalServer.UseClientDisconnectedHandler(evt =>
            {
                Console.WriteLine(string.Format("SERVER - Client disconnected {0}", evt.ClientId));
            });
            LocalServer.UseApplicationMessageReceivedHandler(msgEvt =>
            {
                Console.WriteLine(string.Format("SERVER - Message received from: {0}, topic: {1}, content: {2}", msgEvt.ClientId, msgEvt.ApplicationMessage.Topic, msgEvt.ApplicationMessage.ConvertPayloadToString()));
            });
        }

        private IManagedMqttClient StartClient(string clientid)
        {
            var options = new ManagedMqttClientOptionsBuilder()
               .WithAutoReconnectDelay(TimeSpan.FromSeconds(5))
               .WithClientOptions(new MqttClientOptionsBuilder().WithClientId(clientid).WithProtocolVersion(MQTTnet.Formatter.MqttProtocolVersion.V500).WithTcpServer("localhost").Build())
               .Build();

            var client = new MqttFactory().CreateManagedMqttClient();

            client.UseApplicationMessageReceivedHandler(e =>
            {
                Console.WriteLine("### RECEIVED APPLICATION MESSAGE ###");
                Console.WriteLine($"+ Client = {clientid}");
                Console.WriteLine($"+ Topic = {e.ApplicationMessage.Topic}");
                Console.WriteLine($"+ Payload = {Encoding.UTF8.GetString(e.ApplicationMessage.Payload)}");
                Console.WriteLine($"+ QoS = {e.ApplicationMessage.QualityOfServiceLevel}");
                Console.WriteLine($"+ Retain = {e.ApplicationMessage.Retain}");
                Console.WriteLine();
            });

            client.UseConnectedHandler(e =>
            {
                Console.WriteLine("Client connected successfully {0}", e);
            });

            client.UseDisconnectedHandler(e =>
            {
                Console.WriteLine("Client disconnected {0}", e);
            });

            client.StartAsync(options);
            var topic = "topic1";



            // -------------------- PROBLEM ------------------------------------------
            // works
            //client.SubscribeAsync(new MqttTopicFilterBuilder().WithTopic(topic).WithAtMostOnceQoS().Build());
            // doesn't work
            client.SubscribeAsync(new MqttTopicFilterBuilder().WithTopic(topic).WithExactlyOnceQoS().Build());



            return client;
        }
    }
}

[chkr1011]

The issue is located in the server implementation of MQTTv5.

[chkr1011]

Hi, thanks for reporting this issue. It is a problem with MQTT v5 and will be fixed with the next version. I was able to reproduce it in a new Unit Test.